Separating a double metal cyanide catalyst

Abstract

A method for separating a double metal cyanide catalyst (DMC catalyst) from polyol, comprising: A) initially charging a polyol comprising DMC catalyst, an alcohol, and optionally a filtration aid into a reactor, the mixture being heated, B) filtering the mixture from step A), and C) optionally separating the alcohol from the filtrate of step B), wherein in step A), as the alcohol, 4% by weight to 12% by weight of ethanol, based on 100% by weight of polyol, without a chelating agent is used.

1 . A method for separating a double metal cyanide catalyst (DMC catalyst) from polyol, comprising:
 A) initially charging a polyol comprising a DMC catalyst, an alcohol, and optionally a filtration aid into a reactor, the mixture being heated,   B) filtering the mixture from step A), and   C) optionally separating the alcohol from the filtrate of step B),   
       wherein in step A), as the alcohol, 4% by weight to 12% by weight of ethanol, based on 100% by weight of polyol, without a chelating agent is used. 
     
     
         2 . The method as claimed in  claim 1 , wherein the polyol is a polyether polyol and/or a polyether carbonate polyol. 
     
     
         3 . The method as claimed in  claim 1 , wherein in step A) the alcohol used is 5% by weight to 9% by weight of ethanol. 
     
     
         4 . The method as claimed in  claim 1 , wherein in step A) the mixture is heated to a temperature of from 80° C. to 180° C. 
     
     
         5 . The method as claimed in  claim 1 , wherein in step A) the mixture is heated over a period of from 100 min to 140 min. 
     
     
         6 . The method as claimed in  claim 1 , wherein in step B) the filtration is carried out at a temperature of from 80° C. to 120° C. 
     
     
         7 . The method as claimed in  claim 1 , wherein in step B) the filtration is carried out at a pressure of from 4 bar to 8 bar. 
     
     
         8 . The method as claimed in  claim 1 , comprising the step of
 C) separating the alcohol from the filtrate of step B).   
     
     
         9 . The method as claimed in  claim 8 , wherein the alcohol in step C) is separated off by an evaporation unit, a stripping column, or a combination of these. 
     
     
         10 . The method as claimed in  claim 9 , wherein the evaporation unit is a falling-film evaporator or a thin-film evaporator. 
     
     
         11 . The method as claimed in  claim 1 , wherein the polyol is a polyether carbonate polyol. 
     
     
         12 . The method as claimed in  claim 11 , wherein the polyether carbonate polyol is prepared by addition of carbon dioxide and alkylene oxide onto an H-functional starter compound in the presence of a DMC catalyst, comprising the steps of:
 (α) initially charging a portion of the H-functional starter compound and/or suspension medium not containing any H-functional groups into a reactor, in each case together with DMC catalyst, and optionally removing water and/or other volatile compounds by means of elevated temperature and/or reduced pressure (“drying”),   (β) activating the DMC catalyst by adding a portion, based on the total amount of alkylene oxide employed in the activation and copolymerization, of alkylene oxide to the mixture resulting from step (α), wherein this adding of a portion of alkylene oxide may optionally be performed in the presence of CO 2  and wherein the temperature spike (“hotspot”) which occurs due to the exothermic chemical reaction that follows and/or a pressure drop in the reactor is in each case awaited, and wherein step (β) for effecting activation may also be performed repeatedly,   (γ) adding alkylene oxide and carbon dioxide to the mixture resulting from step (β), where the alkylene oxide used in step (β) may be identical to or different from the alkylene oxide used in step (γ) and wherein H-functional starter compounds and DMC catalyst are optionally metered into the reactor continuously during the addition reaction.